Query Languages

A query can be thought of as a
request of the database, the response to which is
a new table, which I will refer to as a result
table. For instance, referring to the LIBRARY database, we
might request the titles and prices of all books published by Big
House that cost over $20.00. The result table in this case is shown in
Table 5-1.

Table 5-1. Books published by Big House costing over $20.00

Title

Price

PubName

On Liberty

$25.00

Big House

Iliad

$25.00

Big House

Visual Basic

$25.00

Big House

C++

$29.95

Big House

It is probably not necessary to emphasize the importance of
queries, for what good is a database if we have no way to extract the
data in meaningful forms?